Abstract
The flame images were measured by using laser tomography in a spark ignition engine. The curvatures of local flame fronts were computed at each flame boundary. The number of positive curvatures was probably equal to that of negative ones. The average values of positive and negative curvatures were comparable in all flame images. The averaged value of the flame curvatures was smaller than the curvature of equivalent flame radius. The positive and negative curvatures were distributed symmetrically around the zero value.
